Cancer is a major killer throughout the world, and lung cancer is the leading cause of cancer mortality in most countries, causing over 1 million deaths worldwide each year. Further, more than 170,000 newly diagnosed lung cancer cases per year are reported in the United States (Fong et al., Thorax 58:892-900 (2003); Minna et al., Cancer Cell 1:49-52 (2002)).
The incidence of a number of different tumor types has risen in the last two decades. Recently, significant progress has been made in the understanding of molecular genetics of cancer. For instance, proto-oncogenes and tumor suppressor genes are cellular genes that regulate other genes involved in the control of normal cellular growth and differentiation. These genes code for growth factors, growth factor receptors, kinases that phosphorylate diverse cellular substrates, and DNA binding proteins that regulate expression of numerous cellular genes. Oncogenesis may occur through activation of dominant growth promoting proto-oncogenes where mutation (e.g., ras) or overexpression (e.g., Her-2/neu, and c-myc) of the gene product induces malignancy, and inactivation of growth inhibitory tumor suppressor genes (such as p53 and Rb) where the absence of expression or function of these genes results in malignancy. Such cancers have a genetic basis in that the changes responsible for the cancer are at the level of the nucleotide sequence of one or more genes in an individual.
In addition to above genetic changes, cancer also can be caused through epigenetic mechanisms. One epigenetic mechanism involves silencing of gene expression due to methylation of the gene sequence, particularly in CpG-rich regions (CpG islands). Aberrant methylation of normally unmethylated CpG islands has been associated with transcriptional inactivation of defined tumor suppressor genes in human cancers. Epigenetic mechanisms such as methylation silencing of gene transcription provide markers useful for determining whether a cell is susceptible to loss of normal growth control and, therefore, potentially a cancer cell. Cancer often is a silent disease that does not present clinical signs or symptoms until the disease is well advanced. As such, the use of markers that allow the identification of individuals susceptible to a cancer, or even that allow detection of a cancer at an early stage, are of great benefit.
Unfortunately, such markers are not available for most cancers. For example, early non-small-cell lung cancer (NSCLC) is routinely resected with survival rates of 35 to 85%, depending on tumor stage. Unfortunately, most lung cancers are detected late, so that the overall five-year survival rate for NSCLC is only 15%. A major factor in the high mortality of lung cancer patients is the presence of metastatic tumors in approximately two-thirds of patients at time of diagnosis. Detection of cancer in these patients at earlier stages could potentially increase survival rates. DNA methylation detection is a promising approach for identifying lung cancer-specific biomarkers, and it is also a non-invasive method for the detection of biomarkers at an early stage.
The Wnt family of secreted glycoproteins is a group of signaling molecules that is widely involved in developmental processes and oncogenesis (WO 04/032838). The proto-oncogenic effects of Wnt were discovered more than 20 years ago. Since then numerous reports have demonstrated aberrant activation of Wnt signaling pathway in disparate human cancers such as colorectal cancer, head and neck carcinoma (Rhee et al., Oncogene 21:6598-605 (2002)), melanoma (Weeraratna et al., Cancer Cell. 1:279-88 (2002)) and leukemia (Jemal et al., Cancer J. Clin. 54:8-29 (2004)).
Recently, it was reported that Dvl proteins are overexpressed in mesothelioma and NSCLC (Uestema et al., Oncogene 22:7218-7221 (2003)). It was also demonstrated that inhibition of Wnt-1 induces apoptosis and inhibits tumor growth in lung cancer cell lines (Li et al., J. Biol. Chem. 277:5877-81 (2002)). Wnt antagonists can be divided into two groups according to the mechanisms of their functions: the first group includes the secreted Frizzled-related protein (sFRP) family, WNT-Inhibitory Factor-1 (WIF-1) and Cerberus. These antagonists inhibit Wnt signaling by direct binding to Wnt molecules. The second group includes the Dickkopf (DKK) family, which inhibits Wnt signaling by binding to the LRP5/LRP6 component of the Wnt receptor complex (Kawano et al., J. Cell Sci. 116:2627-34 (2003)).
WIF-1 is a naturally secreted Wnt signaling antagonist. WIF-1 is made as 379 amino acid residue protein. WIF-1 has an N-terminal signal sequence of 28 amino acid residues, a unique WIF domain (WD) of approximately 150 amino acid residues, five epidermal growth factor (EGF)-like repeats and a 45 amino aci residue C-terminal hydrophilic domain (Hsieh et al., Nature 398:431-436 (1999); GenBank NP—009122). WIF-1 does not share any similarities with the CRD (cysteine rich domain) of Fz or sFRP (Bui et al., Oncogene 14(10):1249-53 (1997); Melkonyan et al., Proc. Natl. Acad. Sci. USA 94(25):13636-41 (1997); Shimizu et al., Cell. Growth Differ. 8(12):1349-58 (1997); and Todd et al., Cancer Res. 57(7):1344-52 (1997)). WIF-1 has been implicated in the regulation of several developmental processes. For example, it was shown that overexpression of WIF-1 in Xenopus embryos blocks the Wnt-8 pathway and induces abnormal somitogenesis (Hsieh et al., Proc. Natl. Acad. Sci. USA 96:3546-51 (1999)).
Despite advances in the therapy of lung cancer during the past decades, the 5-year survival rate for lung cancer remains under 15%. NSCLC accounts for 75-80% of all lung cancers. A better understanding of molecular mechanisms for lung cancer pathogenesis should improve the treatment of patients with lung cancer. The present invention provides compositions, methods and kits useful for the detection and treatment of cancer wherein WIF-1 expression is down-regulated, such as lung cancer, and for inducing apoptosis in cells wherein WIF-1 expression is down-regulated.